Glycine complexes, with crown ethers

Figure 22-16. Structure of (L)-phenyl glycine (left) and the complex with chiral crown ether (right). (Reprinted from reference 68, with permission.)...

The first attempts at receptors for carboxylate concentrated on protonated polyazamacrocycles. These compounds bind their guests via a combination of electrostatic interactions and hydrogen bonds. An early example of a ditopic receptor composed of a macrocyclic polyamine and crown ether subunit was reported by Kimura. " The triprotonated form of 13 forms 1 1 complexes with zwitterionic compounds, such as glycine. 

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